Apparatus and method of finishing gear teeth

ABSTRACT

Rolled or machine-cut gears are finished by a rolling action in engagement with a die roll comprising a guide gear intermediate a pair of side gears. The outer gears form chamfers on the tooth edges while the guide gear, when working without flank clearance against the work gear, prevents flank bulging and effects smoothing. The teeth of the work gear are substantially confined by the teeth of the three gears of the die roll to prevent bulging of material due to the effect of chamfering as well as effecting burr trimming and smoothing.

. o United States Patent 1 [111 3,729,967 Bauknecht et al. 5] Ma 1, 1973APPARATUS AND METHOD OF [56] References Cited FINISHING GEAR TEETHUNITED STATES PATENTS [75] Inventors: Otto Bauknecht; Adolf Hiirl, bothof 2,271,759 2/1942 Christman ..29/l59.2 Friedrichshafen, Germany3,590,619 7/1971 Sheldon et a! ..29/l59.2 [73] Assignee: ZahnradfabrikFriedrichshafen AG, Primary Examiner Lowen Larson pnednchshafen GermanyAttorney-Zalkind, Horne & Shuster [22] Filed: May 10, 1971 [57] ABSTRACT[2]] Appl. No.: 141,708

Rolled or machine-cut gears are finished by a rolling I action inengagement with a die roll comprising a Foreign pp Priority Data guidegear intermediate a pair of side gears. The outer May 12 1970 Germany..P 20 22 937.2 gears form chamfers the 00th edges While the guide gear,when working without flank clearance n7 2 A against the work gear,prevents flank bulging and efi 2/10 i fects smoothing. The teeth of thework gear are submain 29/159 2 stantially confined by the teeth of thethree gears of 29/96 H 901' the die roll to prevent bulging of materialdue to the effect of chamfering as well as effecting burr trimming andsmoothing.

5 Claims, 5 Drawing Figures Z E 2% i A I l I] I lb.

I F ll i H i J l l l FL% J. L T

Patented May 1, 1973 Fig. 3

I 9 3 0 4 3 3 3, 4 4 6 3 R0 R T N 0 MC T a INVENTORS 0H0 Bauknech! Ado/fH6rl APPARATUS AND METHOD OF FINISHING GEAR TEETH The art of finishrolling gears after having been initially forged or machine-cut, etc.,has already been known. The general method is to roll or machine-cut thework gear to effect a preliminary forming of the teeth of the blank.Thereafter, however, a certain amount of finishing is required for thepurpose of chamfering the edges of the work gear and also deburring theedges and smoothing the flanks. Various machines and methods haveheretofore been known for performing these operations.

For example, it has been known to use a finishing die roll inconjunction with gears which are laterally disposed with respect to thedie roll for effecting chamfering wherein the work gear must be axiallyshifted to come into engagement with each of the side die rolls forsuccessively chamfering and trimming both acuteangled tooth corners ofhelical gear teeth. This arrangement caused bulging at the flanks of thework gear teeth because of flank clearance between the work gear and thedie roll guide gear. The die roll did not prevent such bulging and as aresult, additional operations were required for flank smoothing.

Another machine for chamfering and deburring heretofore known, dispenseswith the guide gear but requires a separate motor for the work gear andfor the chamfering and deburring gears. The chamfer angle must belimited to 35 to avoid bulging of material at the teeth flanks. Also, tomaintain a certain width of chamfer, the rolling time must be limited.For the operation, special instrumentation is required.

Another machine for the purpose combines a motordriven shaving gear witha guide gear both gears meshing with the work gear. The shaving gearremoves bulged material affected by the chamfering action.

Briefly, the present invention avoids the drawbacks of the prior art byproviding a composite die roll comprising a guide gear for meshing withteeth of a work gear to be finished and also comprising a chamferinggear on each side of said guide gear and secured thereto and havingtooth ends at respective tooth ends of said guide gear with chamferingsurfaces at an obtuse angle to said respective. ends, whereby chamferingof tooth corners of said work gear is simultaneously effected by saidchamfering surfaces when said die roll is rotated and by providing meansfor forcing said die roll into a relative radial movement towards saidwork gear, and wherein the teeth of said guide gear are formed to meshwith the teeth of said work gear fully across the flanks thereof andwith zero flank clearance at the end of said radial movement.

A further embodiment of the invention provides a die roll with a guidegear the flanks of which are formed in such a manner and a predeterminedforce being applied to radially move said die roll towards said work andpress the meshing flanks together such that the flanks of said work aresimultaneously smoothed while respective tooth corners are beingchamfered.

By providing a composite die roll of the kind described the chamfering,deburring, trimming and flank smoothing, all can take placesimultaneously. Thus, by applying a confinement to the teeth of the workgear as they are being rolled against the teeth of the composite dieroll, bulging of material at the flanks of the work gear is avoided andno further operational step to remove bulging is necessary.

The invention is applicable to various types of gears, as will bedescribed, and in a simple apparatus wherein the work gear is motordriven while the die roll is freely rotative and moved against the workgear by hydraulic power. Also, the invention is applicable to formedgear blanks not necessarily prepared by a rolling process but by meansof milling, shaping, etc., wherein the invention is capable of acomplete finishing operation.

The flanks of a guide gear intended to smooth the flanks of the workgear can be performed with a profile modification to anticipate adistortion occuring after heat treatment of the finished gears.

In the course of using the invention, rotational direction may bechanged one or more times in order to yield the highest surface qualityand dimensional precision. Further, contact pressure between the workgear and the die roll can be predeterminedly varied to achieve differenteffects for clockwise and counterclockwise rotation.

A detaileddescription of the invention will now be given in combinationwith the appended drawing in which:

FIG. 1 is a fragmentary view of the meeting engagement of teeth of awork gear shown in section with teeth of a composite die roll showingthe guide gear and the chamfer forming gears at the sides thereof,oriented at obtuse angles, the illustration being'for helical teeth, thepresentation of FIG. 1 being illustrative generally of a section on theline A-A of FIG. 4;

FIG. 2 is a view similar to FIG. 1 except that the chamfering die rollgears have teeth which are aligned with the teeth of the intermediateguide gear;

FIG. 3 is similar to the view of FIG. 2 except that the work gear has nohelical tooth angle;

FIG. 4 shows in longitudinal section the essentials of an apparatus forcarrying out the method of the invention;

FIG. 5 is a view similar to FIG. 2, except that all edges of helicoidalwork gear teeth are chamfered.

Reference is now made to FIGS. 1 and 4, and referring initially to FIG.1, a work gear to be finished is comprised of teeth 2 which will beunderstood to be in full mesh with teeth 1 of an intermediate gear of acomposite die roll which intermediate gear is a guide gear and isrotated by the work gear, having zero flank clearance therewith. The dieroll also comprises side or chamfering gears having respective teeth 3and 4. The composite die roll is driven radially by hydraulic power intomesh with the power rotated work gear, as will be more clearlyunderstood from FIG. 4. The chamfering gears comprising teeth 3 and 4are securely festened to the guide gear as shown in FIG. 4, and thechamfering teeth are at a helical angle [3' with the die roll axis. Thehelical angle of the work gear teeth is shown as B. These angles may ormay not be equal, but in any event the angles between teeth 1 and 3, andteeth 1 and 4 are obtuse, as shown on FIG. 1. 7

It should be noted that teeth 2 of the work gear are slightly greater inwidth than the width of the guide gear teeth 1 .of the die roll topermit entry of the lateral ends of the chamfering teeth between workgear teeth.

Upon rotation of teeth 1 and teeth 2 with progressive radial movement ofthe die roll into mesh with the work gear acute-angled corner edges 5 ofthe work gear teeth 2 will be chamfered at diagonally related corners,i.e., at the obtuse vertices interiorly of the angles at the contiguousends of the guide gear and respective inner ends of the chamferinggears. Smoothing due to increased hydraulic pressure acting on the powerrotated work gear is also effected, as well as burr trimming since eachof the work gear tooth flank surfaces is being progressively acted on atthe same time as the chamfering occurs, across the tooth. Reverserotation may be had to further effect the smoothing process.

Upon completion of this operation, it is repeated with chamfering gearsof a helix angle equal to that of the guide gear so as to chamfer thetwo other diagonally related corners of the work gear as described indetail in connection with FIG. 2 and FIG. 3. Thus, the chamfering gearsare removable from the guide gear so that another pair of chamferinggears can be attached to the guide gear, as will be apparent from theshowing in FIG. 4 for the chamfering gears 37 and 38 secured to guidegear 36 as by screws and pins.

Since the guide gear teeth extend the full width of the working flanksurfaces of the work gear teeth full surface smoothing is achieved.Further, very precise smoothing can be effected by reverse rotationcycles at various speeds, and by virtue of the zero clearance thechamfered surface of the work gear corners is held to precise angles andareas.

Referring now to FIG. 2, the die roll guide gear teeth 11 are shown onopposite sides ofa work gear tooth 12, as in FIG. 1, except that thechamfering teeth 13 and 14 are now aligned contiguously with respectiveguide gear teeth 11, and have obtuse angle chamfer surfacescircumferentially offset from the respective guide gear teeth. Thus, theedges or corners of the teeth 13 and 14 are chamfered as at 15 and 16and offset is effected by making the chamfer gear teeth thicker than theguide gear teeth. Accordingly, although the angle ,8 is the same for allteeth, rotation and relative radial motion will cause chamfering of thework gear teeth at both acute-angled flank edges diagonally opposed toeach other.

The chamfering of the work gear teeth is due to the fact that the teeth13'and 14 are somewhat thicker than the teeth 11 and the flank of eachtooth 13 is accordingly circumferentially offset, i.e., extending beyondthe corresponding flank of respective tooth 11. There is an offset inthe opposite direction between teeth 11 and 14. The increased flankthickness extending in opposite direction between teeth 13 and 14 withrespect to the teeth 11 provides for the chamfering engagement as willbe apparent from FIG. 2.

Substituting the gears 13 and 14 by chamfering gears of larger thicknessthe flanks of which are offset with respect to both flanks of the teeth11 of the guide gear as represented in connection with straight spurgears on FIG. 3, will make the chamfered edges 16 to attack and chamferthe adjacent edges in the two other diagonal corners of the work teeth(see FIG. 5).

In FIG. 3, the method is used for straight teeth, all four corners 25 ofwork gear teeth 22-being chamfered simultaneously. In this case, theedges 25 of the chamfering die roll teeth 23 and 24 which face the workgear teeth 22 are all chamfered uniformly at an obtuse angle 'to thetooth flanks. The chamfer gear teeth are thicker and symmetricallydisposed with respect to the guide gear teeth 21 intermediate respectivepairs of chamfer die roll teeth 23 and 24. It will thus be apparent thatif the work gear and die roll are forced into meshing engagement andsimultaneously rotated that all four chamfers 25' will be formed at thesame time and in the same direction of rotation, although reverserotation for flank smoothing by the guide gear may be had.

Referring now to FIG. 4, the apparatus depicted comprises a base onwhich is carried a work gear 31 of width b which will be understood tohave a claw-type ring 32 for keyed engagement with a hub 33 on asupporting flange 35 carried on the base and rotated as by a motordriven shaft 43. Work gear 31 can be secured by a screw 34.

Carried on the base is a slideable carriage 40 in rails 39, reversiblyactuated by a piston rod 41 powered by double ended hydraulic cylinder42. The die roll comprising guide gear 36 and side gears 37 and 38 willbe understood to be a composite and integral assembly freely rotative oncarriage 40.

The width b of the work gear is always somewhat greater than the widthof the guide gear teeth 36 in order to allow space for the action of thechamfering die rolls.

In the course of the operational cycle chamfering and deburring iseffected by the chamfering die rolls and any bulging of material whichmight move by plastic flow to the flanks of the work gear teeth in thevicinity of the chamfering is smoothed out by the action of the guidegear die roll. This is achieved by providing a zero flank clearancebetween the teeth of the work gear and the guide gear die roll in allembodiments of the invention.

While it is contemplated that the invention will be used in conjunctionwith work gears prior to heat treatment it will, of course, beunderstood that the invention is not thus limited but could be used as acold rolling process also for gears made of self-hardening steels.

In particular, the confining effect of the arrangement of the compositedie roll controls the flow of metal in the course of the chamferingoperation so that the finished product needs no further machineprocessing.

We claim:

1. A die roll for finishing gears comprising a guide gear having teethfor meshing with teeth of a work gear to be finished and said guide gearteeth being smaller in width than said work gear teeth; said die rollalso comprising a chamfering gear secured on each side of said guidegear and having chamfering teeth of greater thickness than said guidegear teeth and abutting respective teeth thereof to effectcircumferential offset from the tooth flanks thereof; the teeth of saidguide and chamfering gears being at the same helical angle; chamferedsurfaces on the teeth of said chamfering gears at an obtuse angle to thehelical angle of the guide gear teeth at respective ends thereof;whereby said chamfered surfaces engage the corners ofsaid work gearteeth for chamfering corners simultaneously at both ends thereof as saiddie roll is rotated and moved radially into mesh with said work gear.

2. A die roll as set forth in claim 1, the said greater thickness ofsaid chamfering gear teeth effecting circumferential offset of theflanks thereof in relation to the flanks of respective abutting teeth ofthe said guide gear in both circumferential directions.

3. A die roll as set forth in claim l, said chamfering surfacesextending from the circumferentially offset flanks of said chamferinggears to the corners of the flanks of respective abutting guide gearteeth.

4. A die roll as set forth in claim 2, said chamfering surfacesextending from the circumferentially offset flanks of said chamferinggears to the corners of the flanks of respective abutting guide gearteeth.

5. A die roll for finishing gears comprising a guide gear having teethfor meshing with teeth of a work gear to be finished and said guide gearteeth being substantially the width of the working flanks of said workgear teeth; said die roll also comprising a chamfering gear secured oneach side of said guide gear and having chamfering teeth of greaterthickness than said guide gear teeth and abutting respective teeththereof to effeet circumferential offset from the tooth flanks thereof;the teeth of said guide and chamfering gears being at the same helicalangle; chamfered surfaces on the teeth of said chamfering gears at anobtuse angle to the helical angle of the guide gear teeth at respectiveends thereof; whereby said chamfered surfaces engage the corners of saidwork gear teeth. for chamfering corners simultaneously at both endsthereof as said die roll is rotated and moved radially into mesh withsaid work gear; the teeth of said guide gear being formed to mesh withthe teeth of said work gear up to zero flank clearance whereby theworking flanks of said work gear are simultaneously smoothed while toothcorner thereof are being chamfered.

1. A die roll for finishing gears comprising a guide gear having teethfor meshing with teeth of a work gear to be finished and said guide gearteeth being smaller in width than said work gear teeth; said die rollalso comprising a chamfering gear secured on each side of said guidegear and having chamfering teeth of greater thickness than said guidegear teeth and abutting respective teeth thereof to effectcircumferential offset from the tooth flanks thereof; the teeth of saidguide and chamfering gears being at the same helical angle; chamferedsurfaces on the teeth of said chamfering gears at an obtuse angle to thehelical angle of the guide gear teeth at respective ends thereof;whereby said chamfered surfaces engage the corners of said work gearteeth for chamfering corners simultaneously at both ends thereof as saiddie roll is rotated and moved radially into mesh with said work gear. 2.A die roll as set forth in claim 1, the said greater thickness of saidchamfering gear teeth effecting circumferential offset of the flanksthereof in relation to the flanks of respective abutting teeth of thesaid guide gear in both circumferential directions.
 3. A die roll as setforth in claim 1, said chamfering surfaces extending from thecircumferentially offset flanks of said chamfering gears to the cornersof the flanks of respective abutting guide gear teeth.
 4. A die roll asset forth in claim 2, said chamfering surfaces extending from thecircumferentially offset flanks of said chamfering gears to the cornersof the flanks of respective abutting guide gear teeth.
 5. A die roll forfinishing gears comprising a guide gear having teeth for meshing withteeth of a work gear to be finished and said guide gear teeth beingsubstantially the width of the working flanks of said work gear teeth;said die roll also comprising a chamfering gear secured on each side ofsaid guide gear and having chamfering teeth of greater thickness thansaid guide gear teeth and abutting respective teeth thereof to effectcircumferential offset from the tooth flanks thereof; the teeth of saidguide and chamfering gears being at the same helical angle; chamferedsurfaces on the teeth of said chamfering gears at an obtuse angle to thehelical angle of the guide gear teeth at respective ends thereof;whereby said chamfered surfaces engage the corners of said work gearteeth for chamfering corners simultaneously at both ends thereof as saiddie roll is rotated and moved radially into mesh with said work gear;the teeth of said guide gear being formed to mesh with The teeth of saidwork gear up to zero flank clearance whereby the working flanks of saidwork gear are simultaneously smoothed while tooth corners thereof arebeing chamfered.